|Publication number||US4279306 A|
|Application number||US 06/065,520|
|Publication date||Jul 21, 1981|
|Filing date||Aug 10, 1979|
|Priority date||Aug 10, 1979|
|Publication number||06065520, 065520, US 4279306 A, US 4279306A, US-A-4279306, US4279306 A, US4279306A|
|Inventors||Robert D. Weitz|
|Original Assignee||Top Tool Company, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Referenced by (47), Classifications (9)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The present invention pertains to tools for use in completing oil and/or gas wells. Specifically, it pertains to a washing tool and method suitable for circulating fluid through well conduits and surrounding formations for various treatments thereof.
2. Description of the Prior Art
In completing an oil or gas well after drilling a hole therefor, it is common to install a production casing and to perforate the casing at the producing formation. After completion, the oil and/or gas flows from the formation through the perforations into the production casing where it is usually communicated to the surface of the well through production tubing.
Frequently it is necessary or desirable to treat the formation surrounding the perforated casing in some way to enhance the flow of fluids therefrom. Some methods of treating formations include circulating water or acidized fluid through the formation via the casing perforations and back up the casing string. By such circulation, loose sands may be washed from the formation or consolidated with various materials. Voids may be created for more effective gravel packing, tight formations may be made more susceptible to flow, etc.
In performing such circulating operations, various washing tools have been developed which generally provide some method of packing off an area of the casing for circulation. Such tools are usually attached to the lower end of a washing string, lowered into the casing to the desired depth, packed off and circulating commenced. In most of the tools of the prior art, packing is accomplished by providing packers on the washing tools on opposite sides of the perforations through which the fluid is to flow from the tool. Circulating fluid flows down the circulating string, through the tool, between the packers and out the casing perforations into the formation. Flow then continues back into the casing through perforations above the packers so that the returning fluid flows upwardly through the casing above the tool.
The packers used in washing tools of the prior art are usually of the cup type. Prior art washing tools utilizing cup type packers are made by the Baker Division of Baker Oil Tools, Inc. and Cavins Corporation. Cup type packers leave something to be desired in dependability, failing to adequately seal under many conditions. Furthermore, since the cup type packers engage the casing while the tool is being run into the well or pulled out of it, they are frequently torn or damaged during use.
Upon completion of circulation, it may be desirable to reverse circulate for removing sand or other materials from the bottom of the well hole. This is difficult to effectively accomplish with cup type packers since the packers remain engaged with the casing and since some of them may be flared in a direction which would actually oppose reverse flow. Another problem associated with cup type packers is the possibility of swabbing in the well or pulling sand into the casing when the tool is removed therefrom.
In the present invention a circulating or washing tool and method are provided which eliminate many of the problems associated with cup type packer washing tools. The tool of the present invention includes a tubular mandrel having a flow passage therethrough and the upper end of which is adapted for connecting the tool in a pipe string extending to the surface of the well, the lower end being provided with means for blocking the flow of fluids from the pipe string through the mandrel flow passage. First and second packer assemblies are carried on the mandrel at the opposite ends thereof and an outer tubular body surrounds the mandrel between the packer assemblies. An annular chamber is provided between the mandrel and the surrounding tubular body. The annular chamber is in fluid communication with the mandrel flow passage through ports in the walls of the mandrel and the tubular body is provided with ports which permit fluid communication between the annular chamber and the exterior of the tool.
A valve assembly is carried within the annular chamber blocking the ports in the tubular body and preventing fluid communication between the annular chamber and the tool exterior. However, the valve assembly is responsive to predetermined pressure communicated to the annular chamber through the mandrel ports to unblock the tubular body ports permitting fluid communication between the mandrel flow passage and the tool exterior through the mandrel ports, the annular chamber and the tubular body ports. The packer assemblies are also responsive to a predetermined pressure communicated to the annular chamber through the mandrel ports for actuation thereof. In fact, the packer assemblies are responsive to a lower predetermined pressure than the valve assembly. Thus, the packer assemblies may first be set and then the valve assembly actuated to provide the fluid communication necessary for circulating fluids through the tool for washing the surrounding formation.
The tool is operated by lowering on a pipe string to the necessary level in a perforated casing. Then the lower end of the mandrel flow passage is closed or blocked by suitable means and pressure applied to the annular chamber through the pipe string. Upon reaching a first predetermined pressure level, the packer assemblies are axially compressed and radially expanded until they sealingly engage the walls of the surrounding perforated casing. A further increase in pressure actuates the valve assembly to open tubular body ports and fluids in the pipe string begin to flow to the exterior of the tool through the perforations isolated by the packing assemblies and into the surrounding well strata. The fluid reenters the casing string through perforations above the packer assemblies for return to the surface of the well. After circulation, pressure in the annular chamber is relieved, allowing the valve assembly to close and the packer assemblies to disengage the casing walls. Reverse circulation may be performed to clean sand or debris from the bottom of the hole.
Thus, the circulating or washing tool of the present invention is simple in construction and operation. Due to the hydraulically set packers, it is more reliable than washing tools utilizing cup type packers. Furthermore, such construction permits the tool to be lowered in the well without interference between the packing elements and the casing string so that the packing elements are not damaged on lowering into the well. The tool is short and compact, allowing it to pass through tight areas or slightly out of line casing sections. In addition, after circulation and release of pressure, the packing assemblies are radially contracted for reverse circulation and removal so that there is no danger of swabbing in the well or pulling sand into the casing while the tool is being removed.
Many other advantages of the tool will be understood from reading the specification which follows in conjunction with the accompanying drawings.
FIG. 1 is a sectional elevation view of casing within a well hole showing the washing tool of the present invention in quarter-section and in the unset or running in position; and
FIG. 2 is a sectional elevation view similar to FIG. 1 but showing the tool in its set position for circulation of fluids through the tool and the casing perforations into the surrounding formation.
Referring first to FIG. 1, there is shown the washing tool T of the present invention attached to the lower end of a pipe string P in a perforated casing C of a well having surrounding strata S. The tool T includes a tubular mandrel 1 having a central flow passage 2 therethrough and the upper end of which is provided with means such as threads 3 for connecting the tool to the pipe string P which extends to the surface of the well. The lower end of the mandrel may be threadedly connected at 4 to a ball sub 5 or the like, the purpose of which is to block flow of fluids from the pipe string through the mandrel flow passage when desired. However, in FIG. 1, there is no blockage and flow is permitted through the mandrel flow passage 2 so that if there is any fluid in the casing C, it may be displaced upwardly through the pipe string P as the tool T is lowered into the well. Other tools O, may be attached to the ball sub if desired.
First and second packer assemblies 6 and 7 are carried at opposite ends of the mandrel. These assemblies 6 and 7 will be more fully described hereafter. An outer tubular body 8 surrounds the mandrel 1 between packer assemblies 6 and 7 leaving an annular chamber 9 therebetween.
The annular chamber 9 is in fluid communication with the mandrel flow passage 2 through at least one port 10. The tubular body 8 is provided with a plurality of ports 11 which under certain conditions permit fluid communication between the annular chamber 9 and the exterior of the tool T.
Carried within the annular chamber 9 is a valve assembly, including a differential piston member 12 and biasing spring 13, which in the running position of FIG. 1 blocks the ports 11 preventing fluid communication between the annular chamber 9 and the exterior of the tool. The valve assembly will be more fully described hereafter.
Each of the packer assemblies 6 and 7 includes a tubular packer body 20, 30, which is carried on the mandrel 1 having an annular shoulder 21, 31 and an annular lip 22, 32, thereon. A plurality of resilient packer elements 23, 24, 33, 34, surround the packer bodies 20, 30 adjacent the annular shoulders 22, 32, and may be separated by ring spacers 25, 35. Each packer assembly may also be provided with an annular retainer ring 26, 36 which may also have an annular lip 27, 37, thereon.
Each packer assembly also includes an annular piston comprising an annular head portion 40, 50 and a tubular sleeve portion 41, 51 extending therefrom. The head portion slidingly and sealingly engages the exterior of mandrel 1 and the interior of tubular body 8. The sleeve portion 41, 51 slidingly and sealingly engages the exterior of the respective packer bodies 20, 30. Annular seals 42, 43, 44 and 52, 53, 54 assure sealing at these points of sliding and sealing engagement. It will noted that in the unset position shown in FIG. 1, the head ends of the pistons rest against snap rings 45, 55 attached to the tubular body 8 and the sleeve ends 41, 51 bear against the packer retainer rings 26, 36.
The sleeve portions 41, 51 and the inner diameter of the head portions 40 and 50 of the packer pistons are joined by annular surfaces 46, 56 which along with the sleeve portions 41, 51, mandrel 1 and the ends of packer bodies 20 and 30 form variable annular chambers 47, 57. These variable annular chambers 47, 57 may be vented to the exterior of the tool through longitudinal ports 48, 58 and radial ports 49, 59.
It will also be noted that the packer bodies 20 and 30 are shown attached to the mandrel 2 by threaded connections 20a and 30a allowing removal of the packer body from the mandrel 1. This then would also permit removal of all of the elements of the packer assembly including the packer elements and the packer pistons.
In examining the interior of the tubular body 8, it will be seen that it is provided with a first cylindrical surface 60 and an adjacent second cylindrical surface 61 of slightly smaller diameter. The differential piston 12 of the valve assembly is provided with a corresponding first cylindrical end portion 62 and a second cylindrical opposite end portion 63 of smaller diameter. The end portion 62 slidingly and sealingly engages cylindrical surface 60 of tubular member 8 and the opposite end portion 63 slidingly and sealingly engages a second smaller diameter cylindrical surface 61 of the tubular member 8. Thus the effective annular area exposed to pressure in the annular chamber 9 is greater at the first end portion 62 than at the second opposing end portion 63. Annular seals 64 and 65 assure sealing at these points of contact. At least one relief portion 66 is provided through the walls of the tubular member 8 between the first and second annular seals 64 and 65 through which fluids these seals may be displaced to the exterior of the tool. A small bleed port 67 may be provided in the walls of the tubular member 8 in direct communication with annular chamber 9.
As previously mentioned, the valve assembly includes a biasing spring 13 between the differential piston member and a spring retainer 13a at the fixed snap ring 55. The biasing spring 13 biases the piston 12 toward the position of FIG. 1, blocking ports 11.
To utilize the tool T for circulating operations, it is attached to the pipe string P and lowered into the perforated casing c to the desired depth in the unset position illustrated in FIG. 1. Then a resilient ball member B is dropped through the pipe string P through the mandrel passage 2 for engagement with seating surface 5a of the ball sub 5. (See FIG. 2) This blocks flow at the end of the mandrel flow passage 2. Then, pressure is increased through the pipe string P, fluid entering the annular chamber 9 through mandrel ports 10. As pressure is increased to a first predetermined level, the pressure exerted against the packer piston head portions 40, 50, forces the pistons toward the packing elements 23, 24, 33, 34, axially compressing them between the respective annular shoulders 21, 26, until they are radially expanded to sealingly engage the inner walls of the casing C. Any fluids in the variable annular chambers 47 and 57 are displaced through ports 48 49, 58, 59. The set position of the packers 6 and 7 are shown in FIG. 2.
A further increase in pressure to a higher predetermined level forces the differential piston 12 of the valve assembly downwardly, as viewed in FIG. 2, compressing the biasing spring 13. This is due to the differential pressure area of the piston 12 previously described herein. As the piston 12 moves downwardly, any fluids between seals 64 and 65 are displaced through the relief port 66 and the tubular member ports 11 are opened, as seen in FIG. 2. Fluid then flows from the pipe string P through the mandrel flow passage 2, ports 10, annular chamber 9, and ports 11, to the exterior of the tool. Since the casing is sealed or packed off by the packer assembly 6 and 7, the fluid exiting through the ports 11 continues through the perforations of the casing C between the packer assemblies 6 nd 7 to enter the surrounding well strata S, washing the loose sand or treating the strata in such a way as to create a surrounding zone or area Z for improving the flow characteristics of the well. The circulating fluid and materials carried therewith then reenter the casing C through perforations above the packing assembly 6 where the fluids and entrained materials continue to the surface of the well for disposal.
After it is determined that enough circulation has occurred, pressure is relieved from the pipe string and consequently, the annular chamber 9 of the tool T. As pressure is relieved, the differential piston 12 returns to the blocked position of FIG. 1 due to the reduction in pressure and the force of biasing spring 13. Further reduction in pressure allows the packing elements 23, 24 and 33, 34, to radially contract and axially expand, forcing the packer pistons to return to the initial position of FIG. 1.
If desired, flow can then be reversed down the casing through the perforations above the packing assemblies 6 into the washed out zone Z and around the packing elements 6 and 7 to beneath the ball sub 5. Further circulation will cause the ball B to be displaced to the surface of the well for removal. Reverse circulation may continue off the bottom of the well hole, causing any sand or debris at the bottom of the well hole to be removed from the well through mandrel flow passage 2 and the pipe string P.
The entire tool T may be removed from the well by lifting it on the pipe string P. Since the packing assemblies 6 and 7 are now unset, there is no danger of swabbing in the well or pulling sand into the casing by creating a vacuum therein. Furthermore, the packing elements 23, 24, 34, 31 are not damaged as the tool is removed.
Another feature of the tool of the present invention is the ability to reperforate the well if the first casing perforations are not sufficient, without completely removing the tool. If the ball sub 5 is replaced by a full bore opening valve, this can be done by opening the valve and lifting the tool in the pipe string P for a short distance. Then, a tubing gun can be lowered through the pipe string P, the full opening flow passage 2 of the mandrel and the valve, to a position below the tool T and perforation performed. Then the perforating gun can be removed, the tool T lowered again and circulating repeated. This eliminates the need to completely remove the tool T from the well saving the time necessary for doing so with tools of the prior art.
Thus, it is seen from the foregoing description that the washing tool of the present invention is extremely efficient, easy to use and versatile. Furthermore, it is relatively simple to manufacture and maintain. While a single embodiment of the invention has been described herein, many variations can be made without departing from the spirit of the invention. Therefore, it is intended that the scope of the invention be limited only by the claims which follow.
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|U.S. Classification||166/312, 166/187, 166/147|
|International Classification||E21B33/124, E21B37/08|
|Cooperative Classification||E21B37/08, E21B33/124|
|European Classification||E21B33/124, E21B37/08|